The present invention relates to a drive device incorporating an electric motor for actuating a roller shutter winding tube, for winding and unwinding roll-up members, such as roller-blinds, rolling shutters, sunblinds and the like.
Control devices are known on the market for using an electric motor to drive the winding and unwinding of roll-up members. Control devices of this type are disclosed for example in DE 32 22 770, DE 36 36 855, FR-A-2 775 729, U.S. Pat. No. 5,847,525, WO 00/49264. Additionally U.S. Pat. No. 4,194,266 discloses the use of a planocentric gear assembly in an adjustable roller mechanism for a sliding closure having a case attachable to the sliding closure.
The general structure of these known drive or control devices is illustrated in FIGS. 1 and 2, and substantially comprises an electric motor M, a gear reduction unit R, an electromagnetic (eddy-current) brake unit E and a unit for adjusting the limit switch positions. These components of the control device, as clearly shown in the Figures, are mounted aligned inside of a single winding tube I from one end of which the drive shaft C of the reduction gear protrudes while the other end is rigidly fastened to a first external constraint A1, such as for example the masonry supporting the roller shutter box of a roller-blind. The tube T is therefore subjected to a torsion stress equal to the torque applied when raising the roller member and is designed taking into account the maximum torque supplied by the motor M.
The drive shaft C of the reduction gear, through a pulley to which it is keyed, transmits the rotary motion to a winding tube H on which the roller member is wound or from which it is unwound, with the tube being supported by a friction bearing B1 and by a rolling-contact bearing B2 secured to the tube T and to a second external constraint A2, respectively. On its outer ring the bearing B1 further supports an annular member or crown S for adjusting and centering the tube H inside the tube T. In the known devices the motor M is a single-phase asynchronous motor equipped with two windings, in order to obtain the rotation in both directions. When the motor M is fed, the drive shaft of the reduction gear rotates the pulley G. In turn, pulley G rotates tube H, thus allowing the winding or unwinding of a roller member having one end secured through conventional means to the outer side wall of tube H.
The eddy-current brake unit E is kept in an engagement position by the action of spring means, and is electromagnetically released when electrical power is supplied to the motor M thus allowing the rotation of the motor and the winding/unwinding of the roller member on/from the winding tube.
The control device is completed by a limit switch unit F, usually consisting of one microswitch for each direction of rotation, receiving information about the angular position of the tube H through a thread rod system inside the limit switch unit, with such a system being mechanically controlled by the rotation of the annular member S. The adjustment of the limit switch is achieved by means of screws laterally located on the annular member S or by means of equivalent systems. This way, the limit switch positions of the roller shutter winding tube are established with a maximum accuracy larger than plus or minus 15 degrees of the rotation (angle) of the roller member. In other known systems of limit switch units there are provided electronic systems with an ON/OFF function and in case there is provided for a limitation of the power supplied with a very narrow correction range, in the order of about xe2x88x9230% of the maximum power. In such a case the positioning accuracy of the limit switch can be improved up to a value of about plus or minus 5 to 6 degrees of rotation of the tube H.
These known control devices show nevertheless some drawbacks, among which a loud noise, a low efficiency of operation of the electric motor and a reduced useful life when no maintenance is carried out. Because of these drawbacks, the marketplace acceptance of the devices has been hindered.
The noise is substantially due to the presence of a mechanical speed reduction gear, which is unavoidable for reducing the rotation speed of single-phase electric motors used for these applications, from their standard speed of about 2,000 rpm to the lower speed required to drive the roller shutter winding tube (10-25 rpm). In most cases these reduction gears comprise a planetary three-stage reduction gear units of the type illustrated in the FIGS. 1 and 2. Due to the large number of small-size mechanical parts and/or parts rotating at a high speed, and partially because of an extreme cost-reduction policy (mainly affecting the quality of the materials and the machining tolerances), the reduction gears are source of loud noise and vibrations. Such noise and vibrations increase with the increase of the load applied and with the wear and tear of the device and are further strongly amplified because of their typical location inside of the roller shutter boxes for roller-blinds, generating a so-called resonant, xe2x80x9csound boxxe2x80x9d effect. This is a source of difficulty, especially in domestic applications and when the shutters are moved in the evening and night.
The (low) efficiency of the motor-reduction gear assembly is determined both by the type of the electric motor employed and by the presence of the reduction gear, and is in the order of 10-15% of the drawn power. In addition to a large power consumption, this low efficiency causes motor overheating, thus severely limiting the time for which a device can be continuously operated to a maximum duration of 4-5 minutes. Because of this limitation, there are negative consequences in some application fields such as for example the driving of large sunblinds or roller shutters that are wound on small diameter tubes. An increase of the maximum operation time of the motor would be particularly welcome to guarantee the possibility of carrying out an efficient xe2x80x9cemergencyxe2x80x9d drive under the control of safety devices (for example in the so-called xe2x80x9cwind safetyxe2x80x9d for sunblinds or more generally under the control of signals coming from photocells or similar devices), intervening after a number of consecutive drives that have already increased the motor temperature.
Finally, in the known devices, the mechanical reduction gear is the main cause of a relatively short useful life. This short life is typical for a device operating with satisfactory performance and without maintenance, as it is the case in domestic applications.
The wear of the mechanical rotating parts in the reduction gear frequently induces the generation of loud noise, forcing the replacement of the device or a complete servicing operation after a short operating time.
It is therefore an object of the present invention to provide a drive device for roller shutter winding tubes that is free from the above drawbacks, and more particularly a device generating low noise after a long use, that provides for a better efficiency and therefore causing a low overheating and allowing longer continuous operation times and a maintenance-free, longer useful life.
The above and other objects of the present invention are achieved through a control device for rotating a supporting tube of a roller member to be wound onto or unwound from said tube, said device comprising at least an electric motor housed in said supporting tube and drive means comprising a reduction gear unit for transmitting the rotation from said motor to said supporting tube, wherein said electric motor comprises at least four poles.
Said electric motor is a three-phase electric motor and said device incorporates an electronic unit for feeding in a controlled manner electric power to said motor. Said drive means comprises a single-stage mechanical reduction gear. Said single stage mechanical reduction gear is a planocentric reduction gear comprising a ring gear provided with a given number of teeth, eccentrically and idly mounted on the output shaft of said motor and connected to the output shaft of said reduction gear, said gear wheel meshing with the internal teeth of a stationary ring gear, the number of said internal teeth being greater than said given number, preferably by one tooth.
Additional features of the invention will become evident from the following description of non-limiting embodiments thereof illustrated with reference to the attached drawings.